The present invention relates to a method for fabricating a semiconductor device in which a gate electrode or an interconnect is formed by using a dummy gate electrode or a dummy interconnect.
Recently, in accordance with increased refinement of processing, a dummy electrode or a dummy interconnect is used in order to improve the accuracy in forming a gate electrode or an interconnect.
Now, a conventional method for fabricating a semiconductor device using a dummy gate electrode or a dummy interconnect will be described with reference to drawings.
FIGS. 26A through 26D are cross-sectional views for showing procedures in the conventional method for fabricating a semiconductor device.
First, as shown in FIG. 26A, gate electrodes 12 are formed on a semiconductor substrate 10 having a plurality of pairs of impurity diffusion layers 11 serving as the source or drain regions and selectively formed in surface portions thereof. Each gate electrode 12 is formed on the semiconductor substrate 10 between each pair of impurity diffusion layers 11. At this point, the gate electrodes 12 are densely disposed in a first region R1 on the semiconductor substrate 10 while they are sparsely disposed in a second region R2 on the semiconductor substrate 10. Simultaneously with the formation of the gate electrodes 12, dummy gate electrodes 13 are formed in accordance with the design rule for the gate electrodes 12 in portions of the second region R2 on the semiconductor substrate 10 where none of the impurity diffusion layers 11 and the gate electrodes 12 is formed. Thus, the gate electrodes 12 and the dummy gate electrodes 13 can be disposed uniformly on the semiconductor substrate 10 as a whole. Therefore, photolithography and etching employed for forming the gate electrodes 12 and the dummy gate electrodes 13 can be uniformly carried out, resulting in accurately forming the gate electrodes 12 and the dummy gate electrodes 13.
Next, as shown in FIG. 26B, a first interlayer insulating film 14 is formed over the semiconductor substrate 10, and thereafter, first-layer contacts 15 for selectively connecting the impurity diffusion layers 11 to upper layer interconnects (corresponding to metal interconnects 16 of FIG. 26C) are formed in the first interlayer insulating film 14.
Then, as shown in FIG. 26C, the interconnects 16 of a metal (hereinafter referred to as the metal interconnects) selectively connected to the first-layer contacts 15 are formed on the first interlayer insulating film 14. At this point, the metal interconnects 16 are densely disposed in a third region R3 on the semiconductor substrate 10 while they are sparsely disposed in a fourth region R4 on the semiconductor substrate 10. Simultaneously with the formation of the metal interconnects 16, dummy metal interconnects 17 are formed in accordance with the design rule for the metal interconnects 16 in portions of the fourth region R4 on the semiconductor substrate 10 where none of the first-layer contacts 15 and the metal interconnects 16 is formed. Thus, the metal interconnects 16 and the dummy metal interconnects 17 can be disposed uniformly on the semiconductor substrate 10 as a whole. Therefore, photolithography and etching employed for forming the metal interconnects 16 and the dummy metal interconnects 17 can be uniformly carried out, resulting in accurately forming the metal interconnects 16 and the dummy metal interconnects 17.
Next, as shown in FIG. 26D, a second interlayer insulating film 18 is formed over the semiconductor substrate 10, and thereafter, second-layer contacts 19 for selectively connecting the metal interconnects 16 to upper layer interconnects (not shown) are formed in the second interlayer insulating film 18.
In the conventional method for fabricating a semiconductor device, however, it is necessary to dispose the dummy gate electrodes 13 in consideration of the design rule for the gate electrodes 12 or the impurity diffusion layers 11 as well as it is necessary to dispose the dummy metal interconnects 17 in consideration of the design rule for the metal interconnects 16, the first-layer contacts 15 or the second-layer contacts 19. As a result, the circuit area of the resultant semiconductor device is disadvantageously increased.
In consideration of the aforementioned conventional problem, an object of the invention is preventing the increase of a circuit area in accurately forming a gate electrode or an interconnect by using a dummy gate electrode or a dummy interconnect.
In order to achieve the object, the first method for fabricating a semiconductor device of this invention comprises the steps of simultaneously forming a gate electrode and a dummy gate electrode on a semiconductor substrate; removing the dummy gate electrode; forming an interlayer insulating film on the semiconductor substrate after removing the dummy gate electrode; and forming, in the interlayer insulating film, a plug in a region overlapping with at least a part of a region where the dummy gate electrode has been disposed.
In the first method for fabricating a semiconductor device, after simultaneously forming the gate electrode and the dummy gate electrode, the dummy gate electrode is removed, and then, the interlayer insulating film is formed. Thereafter, the plug is formed in the interlayer insulating film so as to overlap with the region where the dummy gate electrode has been disposed. Therefore, with the accuracy in forming the gate electrode improved by using the dummy gate electrode, the region where the dummy gate electrode has been disposed can be used as the region for forming the plug for selective connection to an upper layer interconnect after removing the dummy gate electrode. Specifically, the area increase of the circuit derived from the use of the dummy gate electrode can be prevented, namely, the circuit area can be as small as that obtained without using the dummy gate. As a result, a semiconductor device having a high degree of integration and high performance can be realized.
In the first method for fabricating a semiconductor device, a photomask used for forming the dummy gate electrode is preferably used in removing the dummy gate electrode.
Thus, the dummy gate can be accurately removed, resulting in improving the reliability of the semiconductor device.
The second method for fabricating a semiconductor device of this invention comprises the steps of forming a pair of impurity diffusion layers serving as source and drain regions in surface portions of a semiconductor substrate; simultaneously forming a gate electrode on the semiconductor substrate between the pair of impurity diffusion layers and a dummy gate electrode on at least one of the pair of impurity diffusion layers; and removing the dummy gate electrode.
In the second method for fabricating a semiconductor device, after forming the gate electrode and the dummy gate electrode on one of the impurity diffusion layers provided on both sides of the gate electrode in the semiconductor substrate, the dummy gate electrode is removed. Therefore, with the accuracy in forming the gate electrode improved by using the dummy gate electrode, the region where the dummy gate electrode has been disposed can be used as a region for forming, for example, a plug for selectively connecting the impurity diffusion layer to an upper layer interconnect after removing the dummy gate electrode. Specifically, the increase of the circuit area derived from the use of the dummy gate electrode can be prevented, namely, the circuit area can be as small as that obtained without using the dummy gate electrode. As a result, a semiconductor device with a high degree of integration and high performance can be realized.
In the second method for fabricating a semiconductor device, a photomask used for forming the dummy gate electrode is preferably used in removing the dummy gate electrode.
Thus, the dummy gate electrode can be accurately removed, resulting in improving the reliability of the semiconductor device.
The second method for fabricating a semiconductor device can further comprise, after the step of removing the dummy gate electrode, the steps of forming an interlayer insulating film on the semiconductor substrate; and forming, in the interlayer insulating film, a plug in a region overlapping with at least a part of a region where the dummy gate electrode has been disposed.
The third method for fabricating a semiconductor device of this invention comprises the steps of simultaneously forming an interconnect and a dummy interconnect on a semiconductor substrate; removing the dummy interconnect; forming an interlayer insulating film on the semiconductor substrate after removing the dummy interconnect; and forming, in the interlayer insulating film, a plug in a region overlapping with at least a part of a region where the dummy interconnect has been disposed.
In the third method for fabricating a semiconductor device, after simultaneously forming the interconnect and the dummy interconnect, the dummy interconnect is removed, and then, the interlayer insulating film is formed. Thereafter, the plug is formed in the interlayer insulating film so as to overlap with the region where the dummy interconnect has been disposed. Therefore, with the accuracy in forming the interconnect improved by using the dummy interconnect, the region where the dummy interconnect has been disposed can be used as the region for forming the plug for selective connection to an upper layer interconnect after removing the dummy interconnect. Specifically, the increase of the circuit area derived from the use of the dummy interconnect can be prevented, namely, the circuit area can be as small as that obtained without using the dummy interconnect. As a result, a semiconductor device with a high degree of integration and high performance can be realized.
In the third method for fabricating a semiconductor device, a photomask used for forming the dummy interconnect is preferably used in removing the dummy interconnect.
Thus, the dummy interconnect can be accurately removed, resulting in improving the reliability of the semiconductor device.
The fourth method for fabricating a semiconductor device of this invention comprises the steps of forming, on a semiconductor substrate, an interlayer insulating film provided with a plug; simultaneously forming an interconnect on the interlayer insulating film and a dummy interconnect on the plug; and removing the dummy interconnect.
In the fourth method for fabricating a semiconductor device, after simultaneously forming the interconnect on the interlayer insulating film and the dummy interconnect on the plug formed in the interlayer insulating film, the dummy interconnect is removed. Therefore, with the accuracy in forming the interconnect improved by using the dummy interconnect, the region where the dummy interconnect has been disposed can be used as a region for forming, for example, a plug for selective connection to an upper layer interconnect after removing the dummy interconnect. Specifically, the increase of the circuit area derived from the use of the dummy interconnect can be prevented, namely, the circuit area can be as small as that obtained without using the dummy interconnect. As a result, a semiconductor device with a high degree of integration and high performance can be realized.
In the fourth method for fabricating a semiconductor device, a photomask used for forming the dummy interconnect is preferably used in removing the dummy interconnect.
Thus, the dummy interconnect can be accurately removed, resulting in improving the reliability of the semiconductor device.
The fourth method for fabricating a semiconductor device can further comprise, after the step of removing the dummy interconnect, the steps of forming a second interlayer insulating film on the interlayer insulating film; and forming, in the second interlayer insulating film, a second plug in a region overlapping with at least a part of a region where the dummy interconnect has been disposed.
The fifth method for fabricating a semiconductor device of this invention comprises the steps of simultaneously forming a virtual gate electrode and a dummy gate electrode on a semiconductor substrate; forming a first resist film on the semiconductor substrate in a region where none of the virtual gate electrode and the dummy gate electrode is formed; removing the virtual gate electrode and the dummy gate electrode; forming a second resist film in a recess from which the dummy gate electrode has been removed; and forming a gate electrode in a recess from which the virtual gate electrode has been removed.
In the fifth method for fabricating a semiconductor device, after simultaneously forming the virtual gate electrode and the dummy gate electrode on the semiconductor substrate, the first resist film is formed in the region where none of the virtual gate electrode and the dummy gate electrode is formed, and then, the virtual gate electrode and the dummy gate electrode are removed. Thereafter, the second resist film is formed in the recess from which the dummy gate electrode has been removed, and then, the gate electrode is formed in the recess from which the virtual gate electrode has been removed. Therefore, the accuracy in forming the virtual gate electrode, namely, the accuracy in forming the gate electrode improved by using the dummy gate electrode, the region where the dummy gate electrode has been disposed can be used for forming, for example, a plug for selective connection to an upper layer interconnect after removing the dummy gate electrode. Specifically, the increase of the circuit area derived from the use of the dummy gate electrode can be prevented, namely, the circuit area can be as small as that obtained without using the dummy gate electrode. As a result, a semiconductor device with a high degree of integration and high performance can be realized.
In the fifth method for fabricating a semiconductor device, a photomask used for forming the dummy gate electrode is preferably used in forming the second resist film.
Thus, the second resist film can be accurately formed in the recess from which the dummy gate electrode has been removed, resulting in improving the reliability of the semiconductor device.
The sixth method for fabricating a semiconductor device of this invention comprises the steps of simultaneously forming a virtual interconnect and a dummy interconnect on a semiconductor substrate; forming a first resist film on the semiconductor substrate in a region where none of the virtual interconnect and the dummy interconnect is formed; removing the virtual interconnect and the dummy interconnect; forming a second resist film in a recess from which the dummy interconnect has been removed; and forming an interconnect in a recess from which the virtual interconnect has been removed.
In the sixth method for fabricating a semiconductor device, after simultaneously forming the virtual interconnect and the dummy interconnect on the semiconductor substrate, the first resist film is formed in the region where none of the virtual interconnect and the dummy interconnect is formed, and then, the virtual interconnect and the dummy interconnect are removed. Thereafter, the second resist film is formed in the recess from which the dummy interconnect has been removed, and then, the interconnect is formed in the recess from which the virtual interconnect has been removed. Therefore, with the accuracy in forming the virtual interconnect, namely, the accuracy in forming the interconnect improved by using the dummy interconnect, the region where the dummy interconnect has been disposed can be used as a region for forming, for example, a plug for selective connection to an upper layer interconnect. Specifically, the increase of the circuit area derived from the use of the dummy interconnect can be prevented, namely, the circuit area can be as small as that obtained without using the dummy interconnect. As a result, a semiconductor device with a high degree of integration and high performance can be realized.
In the sixth method for fabricating a semiconductor device, a photomask used for forming the dummy interconnect is preferably used in forming the second resist film.
Thus, the second resist film can be accurately formed in the recess from which the dummy interconnect has been removed, resulting in improving the reliability of the semiconductor device.